question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Diffraction can be observed in physical waves very easily, however when it comes to the diffraction of electromagnetic waves in things like the single slit experiment, I become a little confused. In things like water, it seems like there is something "holding together" the wave, although I'm not sure what it is. In ... | g14353 | [
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<blockquote>
<p>The frequency applied to a circuit of voltage 120 V with a <strong>real</strong> coil and a resistor has a value of 50 Hz. The resistance of the resistor is 10 $\Omega$. The voltage at the resistor terminals $u_1=60V$. The voltage at the coil's terminals is $u_2=90V$.</p>
</blockquote>
<p>$$\nu=50\te... | g14354 | [
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<p>As far as I've seen, E&M waves are sinusoidal. Our eyes observe these patterns and give us colors, but in a situation like such: <a href="http://physics.stackexchange.com/questions/70054/why-do-electrons-emit-radiation?noredirect=1#comment142793_70054">Why do electrons emit radiation?</a>
There is still a wave, ... | g14355 | [
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<p>The equation for the double slit experiment requires an approximation in naming the two angles used to both be theta, correct? I feel like the majority of equations are exact relations, and it just seems strange that the equation for calculating the maxima an minima doesn't have an exact form.
Is the solution of d*... | g14356 | [
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<p>According to the Pauli principle, there can be no more than two electrons in a given state. If there are a number N of electrons in this box in the lowest states possible, show that the energy of the "top" electron - the "Fermi energy" $E_F$ is $E_F$ = $(2$$\pi$$\hslash$$N)$$/$$2mA$ , where $A$ $=$ $L^2$ and $L$ is ... | g14357 | [
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<p>Why does light continue on forever if it was created from some source whose radiation dwindles at a rate of the inverse square of distance. Clearly light can be viewed as an interdependent phenomena, the E field pulling the B field along with it, but if all light must come from a source, and that source creates a fi... | g14358 | [
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<p>I am in trouble with calculation details of <a href="http://arxiv.org/abs/hep-th/9204083" rel="nofollow">Witten's Two dimensional Gauge Theories Revisited</a>. My questions is about (3.21) and (3.27).
From section 3, we have
$$\delta A_i=i\epsilon \psi_i\\
\delta \psi_i=-\epsilon D_i\phi \\
\delta \phi=0\\
\delta \... | g14359 | [
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<p>I am currently studying a Bachelor of Technology in the subject "Food Technology". I have completed 2 years just now.Yes, I have been exposed to Mathematics in my first year of college studying Differential and Integral Calculus,Ordinary Differential Equations,Linear Algebra, Complex Numbers, Vector Calculus,Probabi... | g14360 | [
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<p>I don't remember enough from my electromagnetism course and I can't find any simple, full example on this subject. </p>
<p>I know, that I can consider the cylinder as a wire with the same charge density (when outside of the cylinder), so I consider the wire case with the same charge density, $\lambda$.</p>
<p>I se... | g14361 | [
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<p>I'm new to electronics. I have a doubt. That is...</p>
<p>Is watt unit depended on speed of turbine ?</p>
<p><strong>In my mind</strong></p>
<p>When turbine rotates fast the power in increase. Is it right ?</p>
<p>Please help me.</p>
<p>Thanks for your response...</p> | g14362 | [
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<h1>Overview</h1>
<p>Einstein's proof for the <a href="http://en.wikipedia.org/wiki/Lorentz_transformation" rel="nofollow">Lorentz transformation</a> is given <a href="http://en.wikipedia.org/wiki/Derivations_of_the_Lorentz_transformations#From_physical_principles" rel="nofollow">here</a>:</p>
<p>From $O$'s view poin... | g14363 | [
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<p>Assume I have built up a pretty high charge by rubbing the floor or something. I want to understand these situations:</p>
<ol>
<li><p>I almost always get shocked when I touch a metal doorknob with my bare hand.</p></li>
<li><p>I occasionally get shocked if I touch the wooden door first, then touch the metal doorkno... | g14364 | [
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<p>I'm trying to scale a physical object up in size, either double or quadruple. It's a circular acrylic plate, with multiple weights attached around it's edge, to lower the resonant frequency to a specific frequency, 32hz. </p>
<p>The plate is 16” in diameter, the weights around it's edge add up to 1.05 kg. It needs ... | g14365 | [
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<p>Suppose we have several antennae to transmit and receive radio waves. What should one transmit, and what kind of equations are used to compute $reflectivity(\vec{x})$ for points in space from a given discretized signal over several antennae?</p> | g14366 | [
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<p>Famously, the path integral of quantum field theory is related to the partition function of statistical mechanics via a Wick rotation and there is therefore a formal analogy between the two. I have a few questions about the relation between the two objects.</p>
<ol>
<li><p>Loop diagrams in quantum field theory hav... | g14367 | [
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<p>We know that a moving charge produces a magnetic field. But which frame of reference it must move to produce magnetic field?
And also if a charged particle moves in a magnetic field, magnetic force acts on it. In which frame of reference it must move to feel a force?</p> | g14368 | [
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<p>In my dynamics notes I have written the following:
$$\frac{d\vec{p}_A}{dt}= \sum\vec{AC_i}\times m\vec{a_{ci}} + \sum \frac{dR_i}{dt}\left\{{I^{(i)}_{ci}}{\omega}^{(i)}_{ci}\right\}+\sum R\left\{{I^{(i)}_{ci}}\frac{d{\omega}^{(i)}_{ci}}{dt}\right\}$$
where $A$ is a random point, $C_i$ the center of mass of object $i... | g14369 | [
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<p>I am trying to model an open system interaction without making strong assumptions on coupling strength or temperature. In general i understand that open systems are modeled by a Lindbladian, but as far as i know the Lindbladian approximation holds only if we have Marcov, Born and Circular Wave approximation. Since I... | g14370 | [
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<p>The closest question I could find with regards to this subject was this one:<br>
<a href="http://physics.stackexchange.com/questions/20730/countersteering-a-motorcycle">Countersteering a motorcycle</a></p>
<p>However, it does not address the specific physics of what I would like to know.</p>
<p>There are 3 ways to... | g14371 | [
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<p>I am learning aerodynamics. In this course a potential flow is denoted that a flow in which the rotation is zero everywhere. But the book told me that we can add vortex into a flow field, and we can also use potential theory to analysis it. I get confused about this. If a vortex is added in a flow field, I don't thi... | g14372 | [
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<p>Like in the question. Why neodymium magnets (Nd2Fe14B) are called "neodymium magnets"? Why not boron magnets? Or iron magnets?</p> | g14373 | [
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<p>A time-varying $B(t)$ field through a loop antenna induces a voltage proportional to $\dot{B}(t)$. A Hertzian dipole along a time-varying $E(t)$ field also induces a voltage across a load--while I haven't seen a rigorous derivation of what it is, since we have a zero output when $\dot{E}(t) = 0$, it seems likely to ... | g14374 | [
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<p>In a laser interferometry experiment, we project a pattern of interference fringes onto a CCD sensor. For best results, we want good contrast between the bright and dark fringes, and we carefully compensate for various sources of noise - for example, by taking camera images with no fringes present, and with the lase... | g14375 | [
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<blockquote>
<p><em>A train rounds a curve of radius 235 m (turning right). The train track is flat, and the train is traveling at a constant speed. A lamp in the train makes an angle to the vertical of 17.5 degrees. How do you calculate the speed of the train?</em></p>
</blockquote>
<p>The first thing I need is to ... | g14376 | [
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<p>Sorry for this very technical question, but we suffer from this problem at work and I do not know any other place to ask. </p>
<p>Its about a good and cheap way of connecting a glass tube with a metal tube in a vacuum setup. There are some solutions with gradually changing glass-materials in order to minimize the t... | g14377 | [
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<p>is there a theoretical limit to the amount of sound energy air can contain? In case, there is a limit, what is that limit? </p> | g14378 | [
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<p>I've always assumed that "quantum locking" was a term invented by the writers of Dr Who, but <a href="http://www.youtube.com/watch?v=Ws6AAhTw7RA" rel="nofollow">this video</a> suggests otherwise.</p>
<p>What is <em>quantum locking</em>? Is it real?</p> | g14379 | [
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<p>I am asked to calculate renormalization for a massless $\phi^3$ theory in $d=6$ dimensional space using dimensional regularization. I'm having trouble finding the three-point vertex correction as one has to choose correct renormalization conditions.
Does anyone know where I can read about this problem?</p> | g14380 | [
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<p>I began wondering about this when working through <a href="http://physics.stackexchange.com/questions/123525/why-should-a-physical-principle-be-applicable-to-different-systems-in-differen/123562?noredirect=1#comment251291_123562">this question</a>: is there anything analogous to spacetime or matter? Both spacetime (... | g14381 | [
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<p>I have a question about the right definition of the <a href="http://en.wikipedia.org/wiki/Green%27s_function" rel="nofollow">Green's function</a> in physics. Why do we introduce (or not) an infinitesimal, positive number $\eta$ to the following definition:</p>
<p>$$\left[ i\hbar\frac{\partial}{\partial t} - \hat{H}... | g14382 | [
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<p><img src="http://i.stack.imgur.com/kWreF.gif" alt="enter image description here"></p>
<p>I don't understand how this could work. So lets say the drive is set to go 30,000,000 meters in a straight line to get to a distant planet. Now lets say the ship size is 20 meters. Now let's make the assumption that the warp... | g14383 | [
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<p>this is a question I had when I was a kid. I'm a bit ashamed because I think I am missing out on something very obvious since I have the same question despite almost being an engineer now!</p>
<p>From Newtonian physics, I understand how although the gravitational force pulls the planet towards a star, and the plane... | g14384 | [
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<p>All books write $X(f)$ in plots - the Fourier transform of $x(t)$ - when they actually mean $\lvert X(f)\rvert$, without even mentioning in passing that they are dropping the mod sign. And also they consider only the mod of FT in the analysis, completely ignoring the phase term - especially communications analysis ... | g14385 | [
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<p>Is <a href="http://en.wikipedia.org/wiki/Velocity" rel="nofollow">velocity</a>:</p>
<ol>
<li><p>Distance/Time in a particular direction, or </p></li>
<li><p>simply Displacement/Time?</p></li>
</ol>
<p>Or both 1 and 2 is the same thing?</p> | g14386 | [
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<p>Suppose that there is a wavefunction $\Psi (x,0)$ where 0 is referring to $t$. Let us also say that $a(k) = \frac{C\alpha}{\sqrt{\pi}}\exp(-\alpha^2k^2)$ is the spectral contents (spectral amplitudes) where $k$ is defined as wavenumber $k$. $\alpha$ and $C$ are constants. </p>
<p>My question is, why do we calculate... | g14387 | [
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<p>I am looking for a way to demonstrate that magnets adhere to the laws of thermodynamics, in particular the requirement that energy in a closed system be conserved.</p>
<p>To adhere to the requirement that energy not be lost, I would expect that the energy required to create a magnet would be offset by the energy ex... | g14388 | [
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<p>I am looking for references (books or web links) which have "simple" examples on the use of group theory in physics or science in general. </p>
<p>I have looked at many books on the subject unfortunately they usually require extensive technical coverage of the basics, i.e. the 1st 100 pages or something, to be able... | g14389 | [
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<p>I was going through a physics book which contains a short description of Nikola Tesla . The description mentioned about poly phase circuits (power supply). Out of curiosity I googled it up and I found that in a poly phase supply we use alternating currents of more than one frequency, say, w1, w2,w3,w4...</p>
<p>Can... | g14390 | [
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<p>Can anyone give a simple explanation for what the fractions and integers mean in particle physics when describing <a href="http://en.wikipedia.org/wiki/Spin_%28physics%29" rel="nofollow">spin</a>?
I've seen on another forum (the naked scientist) that it should not be thought of as angular momentum as described for... | g14391 | [
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<p>I have seen this question:
<a href="http://physics.stackexchange.com/questions/6483/why-can-you-see-virtual-images">Why can you see virtual images?</a> but answers evade the question. Light needs to hit the retina in order, what is the meaning of "dashed" lines in most visualizations that track the light back near t... | g14392 | [
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<p>I understand that general relativity is applicable to gravitational fields and special relativity is applicable to case when there is no gravity. But is there a derivation on how to reduce General Relativity to Special Relativity in limiting case, much like how General Relativity is reduced to Newtonian gravity in w... | g14393 | [
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<p>In Einstein's papers, he used light speed as a reference speed. What if we use a greater finite speed and do the same calculations. Won't this greater speed then be the limit.</p> | g14394 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/10612/explain-how-or-if-a-box-full-of-photons-would-weigh-more-due-to-massless-photo">Explain how (or if) a box full of photons would weigh more due to massless photons</a> </p>
</blockquote>
<p>It has b... | g143 | [
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<p>In a graph on reflection, can i give the x axis a scale of 4 cms = 10 degrees , and the y-axis a scale of 2 cms = 10 degrees? Will it affect the readings? </p> | g14395 | [
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<p>In 3D, I can calculate the total force due to gravity acting on a point on the surface of the unit sphere of constant density, where I choose units so that all physical constants (as well as the density of the sphere) is 1:</p>
<p>$$F = 4\int_{-1}^1 \int_{-\sqrt{1-x^2}}^{\sqrt{1-x^2}} \int_{-\sqrt{1-x^2-y^2}}^{\sqr... | g14396 | [
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<p>Let us assume that there exists a Hamiltonian that (together with the initial state) describes the whole universe.</p>
<p>Then my question is :
What is the spectrum of this Hamiltonian and what are the multiplicities of the spectrum ?
More precisely, what is the representation of the Hamiltonian in Spectral multipl... | g14397 | [
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<p>I am currently wondering about this famous rule:</p>
<p><img src="http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Daniel_Lenord/righthand.jpg" alt="picture"></p>
<p>Where does it come from mathematically that when you point with your thumb in the direction of the current, your curved fingers will point in the dir... | g14398 | [
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<p>While searching in web regarding whether rate of change of acceleration is possible or not; I came across the concept of <a href="http://en.wikipedia.org/wiki/Jerk_%28physics%29" rel="nofollow">jerk</a>. I want to know whether photons which can be accelerated can also have jerk or not?</p> | g159 | [
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<p>I expand metric $g_{ij}$ about flat space $\delta_{ij}$</p>
<p>$$g_{ij}=\delta_{ij}+h_{ij}$$ </p>
<p>where $|h_{ij}|\ll 1$.</p>
<p>I would like to find $R_{ij}$, to linear order, in terms of $h_{ij}$, but I dont know what terms are negligible. Which $\partial h \partial h$, $\partial h$, $hh, h \partial h $, $\pa... | g14399 | [
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<p>I have thought over this problem but I haven't found the solution: There is an electric charge $q$ at a distance $d$ from a conducting slab with thickness $t$, the problem is to find the potential everywhere, assumming that the slab is grounded. So, on the side of the slab where the charge is I think one may use the... | g14400 | [
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<p>I heard a few times that using them as sunglasses is hurting the eye since UV light is not filtered, but the pupil is wider than it would be w/o wearing them because the visible light is dimmed.</p>
<p>I have always assumed since atmospheric (i.e. not reflected from flat surfaces) sunlight is unpolarised and since ... | g14401 | [
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<p>Due to a previous <a href="http://physics.stackexchange.com/q/76158/6316">question</a>, I am confused with the expectation value of the stress-energy tensor in a 2-D conformal field theory.</p>
<p>Let's take the example of string theory, to sketch the problem.
Defining the action by $S = \frac{1}{2 \pi \alpha'}\in... | g14402 | [
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<p>I am struggling with a problem from classical mechanics. Imagine a massless wheel (to make it simpler) with a mass $m$ fixed to it rolling without slipping on a horizontal ground. If we now try to find the equations of motion of the wheel (for instance the angle $\alpha$ it turns) we will find that all the forces ar... | g14403 | [
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<p>What practical application can we expect from particle physics a century or two from now? What use can we make of quark-gluon plasmas or strange quarks? How can we harness W- and Z-bosons or the Higgs boson? Nuclear physics has given us nuclear plants and the promise of fusion power in the near future. What about pa... | g14404 | [
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<p>This question <a href="http://physics.stackexchange.com/questions/7421/brachistochrone-problem-for-inhomogeneous-potential">Brachistochrone Problem for Inhomogeneous Potential</a> has the obvious extension. Namely the same question, when gravity is treated according to general relativity. To make it specific let's c... | g14405 | [
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<p>In the Cohen-Tannoudji Quantum Physics book, Complement BII, says:</p>
<p>[...] two operators $A$ and $B$ with both commute with their commutator. An argument modeled on the preceding one shows that, if we have:</p>
<p>\begin{align}
[A,C]=[B,C]=0
\end{align}
with $C=[A,B]$, then:
\begin{align}
[A,F(B)]=[A,B]F'(B)
... | g14406 | [
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<p>I'm a computer programmer that never studied physics in school and now it's coming back to bite me a bit in some of the stuff I'm being asked to program. I'm trying to self study some physics and I've got a few open source intro physics books and understanding it for the most part but I'm a bit confused on this sta... | g14407 | [
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<p>We know, the rockets in space use Newton's 3rd law to increase their velocity and hence move. What I don't understand is how it is possible in space aka vacuum-state without air? From what I know, Joule's "Free Expansion of Gas" says that free-expansion compresses the gas and is therefore "affected" by vacuum so it ... | g14408 | [
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<p>Earth moves with a speed around $100000 \,\,km/h$, which will be amazing, but from where we can see that moving speed? If we far away from earth (outside of earth gravity) then can view its moving? is any video already taken? (I failed to search that kind of video).</p> | g14409 | [
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<p>Is it possible to demonstrate that there are just 14 types of Bravais lattice without the knowledge of group theory?</p> | g14410 | [
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<p>The "equal angles" law of refection on a flat mirror is a macroscopic phenomenon. To put it in anthropomorphic terms, how do individual photons know the orientation of the mirror so as to bounce off in the correct direction?</p> | g92 | [
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<p>If something is moving away fast it's color would appear redder than its actual color due to phenomenon known as Doppler effect. </p>
<p>But what if the object isn't moving but i am moving away faster would that still affect the way waves travel. </p>
<p>Optional:-</p>
<p>And why. Object emitting isn't moving. An... | g14411 | [
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0.0385834239423275,
0.04853319749236107,
0.063645... |
<p>We have discovered quite a number of exoplanets to date. The Kepler spacecraft has examined 150,000 stars and found <a href="http://exoplanet.eu/catalog/">1,059 exoplanets</a>.</p>
<p>We know that Kepler, as well as all other exoplanet searches to date, can only find planets that cross in front of their star. That ... | g14412 | [
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<p>In Landau-Lifschitz, following expansion is given,
We have,
$$L(v'^2)~=~L(v^2+2\textbf{v}\cdot\epsilon+\epsilon ^2)$$
expanding this in powers of $\epsilon$ and neglecting powers of higher order,
$$L(v'^2)~\approx~L(v^2)+\frac{\partial L}{\partial (v^2)}2\textbf{v}\cdot\epsilon$$</p>
<p>$L$ is Lagrangian. and $\te... | g962 | [
0.04472966492176056,
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<p>How can I derive the following formula?
$$\int d^{d+1} k \frac{e^{i K X}}{K^2} = \frac{\Gamma (d-1)}{(4\pi)^{d/2} \Gamma (d/2) |X|^{d-1}}, \quad K^2 = k_0^2 + \vec k^2, KX = k_0 \tau + \vec k \vec x$$
What I tried so far:</p>
<ol>
<li><p>Integrate over $k_0$ while promoting $k_0$ to complex variable, so I can use ... | g14413 | [
-0.06280465424060822,
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0.034656770527362823,
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0.03947072476148605,
0.08736710995435715,
0.0... |
<p>In physics entropy is usually measured in <a href="http://en.wikipedia.org/wiki/Nat_%28information%29" rel="nofollow">nats</a>. I wonder is there a possible model of a physical system which has entropy of discrete number of nats?</p>
<p>How particles and degrees of freedom should be arranged so this to happen?</p>
... | g14414 | [
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-... |
<p>I have recently been intrigued by the following question: What is the difference between the pitch of the noise of dripping water between hot and cold water? For example, would cold water create a higher pitched noise while dripping into a pot of water? Or vice versa?</p> | g14415 | [
0.08094276487827301,
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<p>In the <a href="http://web.njit.edu/~kappraff/chapter19.pdf" rel="nofollow">this</a> chapter of an online pdf we are given an equation for the deflection of a beam:
$$\frac{d^2y}{dx^2}=\frac{\overline{M}}{E I}$$
where $E$ is the modulus of elasticity, $\overline{M}$ is the moment as function of $x$ and $I$ is the mo... | g14416 | [
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0.03272666782140732,
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... |
<p>Let's start with kinetic energy (from <a href="http://en.wikipedia.org/wiki/Kinetic_energy">los Wikipedias</a>)</p>
<blockquote>
<p><em>The kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated ... | g14417 | [
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<p>Photons of relic radiation loose their energy as they propagate through space. Will a space traveler loose their peculiar velocity as he travels through vast distances? Will he stop somewhere or still he would be able to reach the stars at unlimited distance without burning the engines?</p> | g14418 | [
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<p>Saw a question about faster than light travel... I still have the same question though none of the answers offered any resolution for me.
It is so summarily assumed by all physicists and commentaries that exceeding the speed of light would turn back the clock. I can't see the relation. </p>
<p>Doubling the amount ... | g14419 | [
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<p>There are no book recommendations for Astrophysics here. I will write my own answer, but I am also interested in what are others' views on the question (I will NOT mark my own answer as the best one).</p> | g741 | [
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<p>Reading <a href="http://physics.stackexchange.com/questions/1019/common-false-beliefs-in-physics">Common false beliefs in Physics</a> I feel that there are also "fake false beliefs", ie, that the "false belief" does not actually exists, it is a rhetorical argument or just a basis for argumentation, but not actually ... | g14420 | [
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<p>Could you please recommend a sufficiently elementary introduction to K3 gravitational instanton in general relativity and the problem of finding its explicit form?</p>
<p>Under 'sufficiently elementary' I mean the texts geared at physicists with basic knowledge of general realtivity but not much more than that (i.e... | g14421 | [
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0.052211809903383255,
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... |
<p>In case of the gauge-fixed Faddeev-Popov Lagrangian:
$$ \mathcal{L}=-\frac{1}{4}F_{\mu\nu}\,^{a}F^{\mu\nu a}+\bar{\psi}\left(i\gamma^{\mu}D_{\mu}-m\right)\psi-\frac{\xi}{2}B^{a}B^{a}+B^{a}\partial^{\mu}A_{\mu}\,^{a}+\bar{c}^{a}\left(-\partial^{\mu}D_{\mu}\,^{ac}\right)c^{c} $$</p>
<p>(for example in Peskin and Schr... | g14422 | [
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<p>I am trying to reproduce the number of participants $N_{part}$ in Pb-Pb Collisions at LHC using a Glauber Monte Carlo simulation, specifically aiming to reproduce the values given in <a href="http://prl.aps.org/abstract/PRL/v106/i3/e032301" rel="nofollow">Phys. Rev. Lett. 106, 032301 (2011)</a> by K. Aamodt et al. (... | g14423 | [
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<p>In a rectangular room 10*8*5 how can the eigen modes belonging to octave and third octave bands centered at 50Hz be found ? I have the formula to calculate the number of modes but don't have the idea how to find the modes. Do I need to use Matlab for it ?</p> | g14424 | [
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<p>This <a href="http://www.physicsclassroom.com/class/estatics/Lesson-4/Electric-Fields-and-Conductors" rel="nofollow">site</a> says that if the field at the surface at the conductor has a parallel component, then the surface charge will move, which is impossible if the conductor is at equilibrium. </p>
<p>But I lear... | g14425 | [
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0.04632127657532692,
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<p>An electric lamp having coil of negligible inductance connected in series with a
capacitor and an AC source is glowing with certain brightness. How does the
brightness of the lamp change on reducing the (i) capacitance, and (ii) the frequency ? What if the diaelectric slab is introduced between the capacitor.</p> | g14426 | [
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<p>Is the Virgo Supercluster affected at all by the expansion of space? What about the larger filament that Virgo resides in?I don't quite understand how gravity affects space time locally in groups of galaxies, and am wondering if the expansion of space is lumpy. It would be nice to know we are not all being stretched... | g14427 | [
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<p>Let's say there is a charged tube(cylinder with no top or bottom) with radius $a$, length $l$ and charge $q$ and a point which is collinear with the centre of the charged tube. Anyway, since we can think the tube as infinite charged rings we first should calculate the electric field of a single ring.(the distance be... | g14428 | [
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<p>Our measure of distance (the meter) is defined in terms of how far light in a vacuum travels in a specific time.</p>
<p>When light travels through another medium, we say it travels at a different speed. Why not say it travels at the same speed, and the distance in the medium is different that the distance outside? ... | g14429 | [
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<p>When doing calculations in rigid body mechanics, it is necessary to choose an origin to calculate torques and angular momenta. However, the underlying dynamics does not depend upon the choice of that origin. This is very reminiscent of gauge theories. Could we interpret the choice of origins as a gauge fixing? Has g... | g14430 | [
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<p>I've already tried to find the expression but I don't find the expected result for the quantity of charge when I use the expression I found. For example, I checked it by integrating the expression that I found from $r=0$ to $r=\frac{L}{2}$, it should lead to $Q=\frac{\lambda L}{2}$ but it is not what I find.</p> | g14431 | [
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0.042012... |
<p>The capacitor has insulator and it is covered by two conductors from top and bottom.
I started to think if this insulation part can be wide like 1 cm big - yes, it can but then permittivity has to be great for great capacitance. </p>
<p>If the insulator is air, then I think the capacitor is very weak.
Capacitance ... | g14432 | [
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... |
<p>The string theorist Brian Greene recently came up with the book The Hidden Realities. In Chapter 9, and also in the article <a href="http://discovermagazine.com/2011/jun/03-our-universe-may-be-a-giant-hologram" rel="nofollow">http://discovermagazine.com/2011/jun/03-our-universe-may-be-a-giant-hologram</a> , he argue... | g14433 | [
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<p>I am an electronics and communication engineer, specializing in signal processing. I have some touch with the mathematics concerning communication systems and also with signal processing. I want to utilize this knowledge to study and understand Quantum Mechanics from the perspective of an engineer. I am not interest... | g14434 | [
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<p>A friend of mine was telling me about a storm that knocked down a power line over at their place, and it got me to thinking. Why are downed power lines dangerous? I don't see any good reason for it.</p>
<p>It seems to me that if they can put a <a href="http://en.wikipedia.org/wiki/Ground-fault_current_interrupt" ... | g14435 | [
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<p>What is the phase shift of a wave that tunnels through a barrier, meaning the difference in phase between the incoming (in front of the barrier) and the outgoing (behind the barrier) waves?</p>
<p>For example, in the situations of a wave function tunneling through a classically forbidden region, where the wave is n... | g14436 | [
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<p>I'm trying to understand how symmetry groups are related to potentials of the Schrodinger equation. In particular, I wish to know if it is possible to find the symmetry group of this potential
$$V(x) = A_0 +A_1x +A_2x^2 -\frac{9}{4}x^4$$</p>
<p>where $A_0$,$A_1$,$A_2$ $\in \mathbb{R}$</p>
<p>I've tried to see if ... | g14437 | [
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<p>I am having difficulty grasping the concept of a <a href="http://en.wikipedia.org/wiki/Longitudinal_wave" rel="nofollow">longitudinal wave</a>. My textbook definition "In longitudinal waves, the vibration is backwards and forwards in the direction of motion of the wavefront"</p>
<p>If it vibrates backwards and then... | g14438 | [
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<p>The Venusian atmosphere is according to CalTech's webpage <a href="http://coolcosmos.ipac.caltech.edu/ask/43-What-is-the-atmosphere-of-Venus-like-" rel="nofollow">What is the atmosphere of Venus like?</a> is 90 times heavier, than Earth's, containing predominantly carbon dioxide, some nitrogen, sulfuric acid clouds ... | g14439 | [
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<p>I was sitting in my parked car tonight when a Harley-Davidson motorcycle parked next to me. With my window down, I could hear that as the motorcycle was cooling down, it was giving off some type of “popping noises.” My first guess was that as the metal of the exhaust pipes cooled, thermal contraction occurs such tha... | g14440 | [
0.09723006933927536,
0.028065234422683716,
0.009496876038610935,
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0.05619457736611366,
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0.050760067999362946,
0... |
<p>For example because of newton law $F=ma$ force is acceleration times mass but if I go at a high constant velocity ($900\: \mathrm{miles/hour}$) in my car for examples I have $0$ acceleration but if I hit an obstacle by newton's law it will have no effect on me because $F=ma$ and mass of my car x 0 = 0</p>
<p>But i... | g14441 | [
0.028717124834656715,
0.041174259036779404,
0.02766372263431549,
0.04678896442055702,
0.0672706589102745,
0.0479838103055954,
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0.07678823173046112,
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0.0011378434719517827,
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-0.00528370... |
<p>I am trying to solve a challenging problem, and I'm hoping for some advice on how to proceed. I want to model sound waves in a cavity for the purpose of determining resonance. The plan is to answer the question numerically, but I need some better bearings regarding the physics involved.</p>
<p>Here is a summary o... | g14442 | [
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0.021127738058567047,
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0.013505512848496437,
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0.007629156578332186,
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0.01225457526743412,
0.028004677966237068,
0.0... |
<p>I am wondering, when we change the resistance in a circuit, does the voltage tend to increase or the ampere decrease? More specifically, under what conditions does what happen?</p>
<p>E.g. If we have a high-resistance voltmeter, does increasing the resistance of the circuit itself necessary increase the reading, or... | g14443 | [
0.0070184883661568165,
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0.0006632194854319096,
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0.05512723699212074,
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0.0561559833586216,
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0.030308710411190987,
-0.036402858793735504,
... |
<p>What is the reference spectrum? I need to know how to calculate the reference spectrum of a wavelength 500nm. </p> | g14444 | [
-0.02433144487440586,
-0.04740520939230919,
0.005409639328718185,
-0.03823433816432953,
0.027071721851825714,
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0.01746116578578949,
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0.007184990681707859,
0.07694029062986374,
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0.03... |
<p>Why adding just one electron changes tremendously the ionization potential from any of the nobel atoms ? </p>
<p>If it is the screening why adding a second electron increases the ionization potential ?
<a href="http://en.wikipedia.org/wiki/File:IonizationEnergyAtomicWeight.PNG" rel="nofollow">http://en.wikipedia.o... | g14445 | [
0.027409227564930916,
0.07526174932718277,
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0.013438460417091846,
0.012667510658502579,
0.042149994522333145,
0.014808330684900284,
0.0145375... |
<p>The higher the quantum number(energy levels)m the higher the energy.
What does the energy refers to? Kinetic energy, potential energy, or the total mechanic energy?</p> | g14446 | [
0.05580447241663933,
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<p>For a localized charge distribution the potential is set to zero far away from the charge distribution (at infinity)</p>
<p>Now, when grounding a conductor, i.e. connecting it to Earth, it is said that we are setting its potential to zero. </p>
<p>Why Earth's potential is zero?
And if it is zero, is it zero even i... | g14447 | [
0.08310984820127487,
0.0430767759680748,
0.016259385272860527,
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0.059166859835386276,
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0.027801308780908585,
0.06941691040992737,
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-0.02739669382572174,
-0.00243... |
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